Roadside reflective markers are well known to alert a driver to visually imperceptible or obscured objects, or to call attention to construction sites, upcoming road signs, and the like. Because visibility in periods of darkness (e.g., at night) is important, these markers are made to reflect incident light rays, such as light from automobile headlamps.
There have been introduced over the years numerous types of reflective markers. One kind includes a stationary reflective element. A drawback of stationary reflective markers, however, is that most reflectors only reflect light at small angles of incidence. In the exemplary situation of roadside reflective markers, if an automobile's headlamps are not aligned properly with the reflective marker then light is not reflected back to the automobile. In such circumstances, the reflective marker is practically useless. To address this problem, reflective markers have been introduced having a reflective element rotatable about an axis to provide optimum visibility in 360 degrees of rotation. It is known that the reflective element in such devices may be rotatable by wind, for example from passing vehicles. Roemisch, U.S. Pat. No. 2,693,044, is exemplary. In conditions of no or low wind, however, the reflective element will not rotate and the marker becomes of no more benefit than an ordinary stationary marker. In high wind conditions, conversely, some conventional wind-driven reflectors may rotate too quickly and decrease the eye-catching visual effect of the rotating feature.
Still other reflective markers have reflective elements exposed to the elements, such as taught by Slaughter, U.S. Pat. No. 4,747,664. Exposed reflectors are prone to become damaged, worn, and/or covered with dirt, thereby reducing their visibility.
Other known rotatable reflective markers include electro-mechanical drive means to ensure operability even in conditions of little or no wind. Some types of these known markers require an external power source, such as a conventional electrical outlet. However, an external power source may not be readily available in all circumstances. Still other such electro-mechanical reflective markers use an internal source, such as a conventional, non-rechargeable battery, that must be frequently replaced. Still other devices, such as Malgarin, U.S. Pat. No. 4,183,622, teach the use of solar power. Malgarin specifically discloses a solar beacon having application as an aircraft anti-collision device. The Malgarin device is taught, in one embodiment, to employ a drive motor for rotating the beacon's reflector, the drive motor powered by an array of solar cells. However, this beacon does not operate during periods of darkness.